Many apparatuses have been developed for storing, letting out, and reeling in waterski tow ropes by providing motorized reels that are mounted either inboard or outboard on the back of a waterski boat. Several such tow rope reel apparatuses are disclosed in the following patents: U.S. Pat. No. 3,919,963 to Cox, III; U.S. Pat. No. 3,420,466 to Sanders; U.S. Pat. No. 3,034,742 to Reynolds; U.S. Pat. No. 2,915,259 to Force; and U.S. Pat. No. 2,816,310 to Nale. However, the apparatuses disclosed in these patents are disadvantageous because they only provide a single tow rope for a single waterskier.
This disadvantage has been overcome by the development of several tow rope reel apparatuses that include more than one spool, accordingly providing more than one tow rope, so that a number of waterskiers can ski behind the same boat simultaneously. For example, U.S. Pat. No. 3,195,831 to Shriner et al.; U.S. Pat. No. 3,043,259 to Sadler; and U.S. Pat. No. 3,003,453 to Jamieson all disclose waterski tow rope reel apparatuses that have multiple spools with multiple tow ropes. However, a circumstance that must be taken into consideration when more than one waterskier is towed behind a single boat is the danger created when one skier falls or lets go of his/her rope while the other skier remains up. The tow rope that has been dropped can pose a hazard to the skier who remains up and continues to ski. Therefore, it is desirable to provide a means for reeling in the tow ropes independently of one another so that an unattended tow rope can be removed from the path of a skier who is still skiing.
The patent to Sadler discloses one method of providing tow rope independence, which is to simply provide two independently operating tow rope reel apparatuses, each having its own motor, driveshaft, and spool. Each tow rope reel apparatus disclosed in the Sadler patent also includes a solenoid-operated mechanical linkage that engages and disengages the spool from the driveshaft using male and female spline gears. This method of providing tow rope independence is disadvantageous, however, because many components such as the motor are redundant. Two entirely independent reel apparatuses, one for each tow rope and skier, add weight and bulk to the waterski boat and are more costly than necessary.
The approach taken by Shriner et al. and Jamieson is more efficient than that of Sadler. As disclosed in the Shriner et al. and Jamieson patents, a single motor is used to drive multiple spools. However, if only one motor is used to reel in both tow ropes, the multiple spools must still be independently operative so that the aforementioned danger of waterskiing alongside an unattended tow rope trailing behind the boat is avoided. The apparatus disclosed in the patent to Shriner et al. retrieves two waterski tow ropes either simultaneously or independently of each other by using differential gearing.
The patent to Jamieson discloses a ski rope reel apparatus that includes a single motor, a single driveshaft, and three spools. This apparatus automatically retrieves any unattended ropes and can retrieve ropes simultaneously or independently of each other by employing a "friction clutch" for each spool so that the spools can rotate independently of each other. Each friction clutch consists of a pair of opposing semi-circular shoes, one of which is attached to the respective spool, that frictionally embrace the driveshaft to transfer force from the driveshaft to the respective spool. In the operation of the Jamieson apparatus, from one to three waterskiers can pull the tow ropes from the spools, which slip on the friction clutches as they are unreeled due to the pull exerted by the skiers. The ski boat to which the apparatus is attached will then taxi away until the full lengths of the tow ropes are let out from the spools. If one or all of the waterskiers falls or lets go of his/her tow rope, the boat operator can actuate the motor to rewind the unattended tow ropes onto the spools. However, if one or two skiers remain up and continue to ski, tension on these attended tow ropes prevents them from being reeled in. The driveshaft will slip within the friction clutch shoes associated with these spools and the spools still trailing skiers will not rotate; only the spools with unattended tow ropes will rotate.
While the Jamieson apparatus is advantageous in that it permits a number of waterskiers to ski behind the same boat simultaneously and in that it independently reels in the tow ropes, the configuration of this apparatus has several disadvantages. First, the friction clutches employ shoes that tend to wear out over time, much like automotive brake shoes or clutch disks. The clutch shoes on the Jamieson apparatus must therefore be periodically replaced for the Jamieson apparatus to function properly and safely. Worn clutch shoes could result in unattended tow ropes not being reeled in or being reeled in too slowly, posing the aforementioned hazards to other skiers. A second disadvantage of the Jamieson design is that because the friction clutches require just that, friction, wet clutch shoes tend to impair the functioning of the friction clutches. Because the tow rope apparatus is used on a waterski boat and is constantly doused with water, the friction clutches will inevitably become wet and lose their effectiveness similarly to wet brake shoes on a car. Like worn clutch shoes, wet clutch shoes can result in the dangerous situation of unattended tow ropes not being reeled in, or at least being reeled in too slowly. A third disadvantage is that the friction clutches add considerable bulk and length to the Jamieson apparatus. The friction clutches are disposed beside the respective spools around the driveshaft; therefore, the spools must be separated by some distance and cannot be disposed side-by-side immediately adjacent to one another to give rise to a compact configuration. A fourth disadvantage is that a certain threshold amount of pull must be exerted on the tow rope of each spool to overcome the friction clutch, breaking its grip on the driveshaft, and unwind the tow rope from the spool. This presents problems for beginning waterskiers who must concentrate both on standing up in the water while simultaneously pulling on the tow rope. Beginning waterskiers learn more quickly if they only have to worry about one thing at a time; therefore, the friction clutches disclosed in the prior art complicate the learning process for beginning skiers.
Another waterski tow rope reel apparatus that employs a friction clutch is disclosed in U.S. Pat. No. 2,956,778 to Weide. This patent discloses an apparatus that includes only one spool with an adjustable friction clutch mechanism for transferring power from a driveshaft to the spool. The friction clutch mechanism includes a number of friction discs and plates that cooperate with each other to turn the spool. A washer-nut is hand tightened to adjust the amount of slip in the clutch to thereby vary the power transferred to the spool. However, this apparatus is disadvantageous not only because it can be used by only one waterskier but also because it is subject to the same problems with friction surface wear and wetness detailed above with regard to the Jamieson apparatus.
Thus, there remains a need for a new and improved waterski tow rope reel apparatus that can be used to tow more than one waterskier simultaneously while at the same time being able to independently reel in only an unattended tow rope while leaving out a tow rope being used by a waterskier.